How exactly this can be done? There must be some NAND flash memory somewhere. It is possible to reprogram flash memory using good old LPT port from the PC? I can make some stuff with ATMEGA controller btw

I do NOT support "latest fw" at ALL. If you have one you should block updates on router and wait for it to STOP being "latest":)If you want me to help you please paste FULL log(s) to "spoiler"/"code" bbcodes or provide link(s) to pasted file(s) on http://ctrlv.it/ Otherwise "NO HELP"!!!If you want root DISABLE internet access to your device!!!!DO NOT EVER INSTALL FIRMWARE UPGRADE !!!!